The invention relates generally to locking devices that prevent unauthorized actuation of a system in which the device is included, and more particularly to locking devices that prevent unauthorized release of the brakes on a vehicle.
The prevention of theft of expensive equipment, such as heavy trucks or semi-tractors, has spawned the development of various anti-theft devices for such equipment. Such prior devices have proved to be inordinately difficult and cumbersome to use or largely ineffective in preventing the defeat of the system by a thief. In addition, many of such prior anti-theft systems are designed to interrupt either the braking system or the electrical system in such a way that could result in a dangerous situation in the event of failure of the anti-theft device while the vehicle was operating. Therefore, the need has arisen for a substantially effective anti-theft system for vehicles that will cause no danger to the vehicle or its operator in the event of failure of any of its components.
In accordance with the invention, an anti-theft device for a vehicle includes a moveable lock member biased into interfering engagement with a brake actuating member when the actuating member is moved to a brake-applied position. The lock member thereby prevents release of the brakes until a selectively operable release system is activated in response to operation of the keyed switch for the ignition system. Preferably, the anti-theft device also includes a timer circuit which de-activates the release system, thereby preventing the vehicle from being moved, if the brakes are not released within a predetermined time period. The timer apparatus may also prevent the release system from being activated more than a given number of times within a second predetermined time period and may also include means for reprogramming the timing sequence of operation of the anti-theft device or the durations of the first and second time periods. The anti-theft device and the timer apparatus are housed in a substantially tamper-proof housing which is preferably hidden from view and not easily accessible to a potential thief.
The invention may also include an alarm system which would be activated in the event of improper operation of the anti-theft device, thereby indicating an attempted unauthorized operation of the vehicle.